1. Field
The subject matter disclosed herein relates to circuits and systems for processing analog signals.
2. Information
To recover information from a signal received from noisy communication channel, a receiver typically employs filtering and equalization techniques to enable reliable detection of the information. Decreases in the cost of digital circuitry have enabled the cost effective use of adaptive digital filtering and equalization techniques that can optimally “tune” a filter according to the specific characteristics of a noisy communication channel.
FIG. 1 shows a conventional digital filter 10 employing a finite impulse response (FIR) configuration. An analog input signal 12 is received at an analog to digital converter (ADC) 14 to provide a digital signal at discrete sample intervals. The analog input signal 12 may be transmitting encoded symbols representing information in a noisy communication channel. The ADC 14 may sample the analog input signal at discrete sample intervals corresponding with an inter-symbol temporal spacing or fractions thereof. The sampled output of the ADC 14 comprises a digital signal plus noise. On each discrete sample interval, the digital signal from the present discrete sample interval is provided to a multiplication circuit 20 to be scaled by coefficient c0, and signal taps from the two previous discrete sample intervals (i.e., the digital signal delayed by delay circuits 16 and 26) are provided to multiplication circuits 20 to be scaled by coefficients c2 and c4, respectively. The outputs of the three multiplication circuits are then additively combined at a summing circuit 22 as a filtered output signal.
The delay circuits 16 and 26 store and forward digital values to provide digital output signals which are delayed versions of digital input signals. For example, the delay circuits 16 and 26 may comprise single or multi-bit latch circuits to provide digital signal taps on an interval T.